package com.hll.filter;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.Map;

/** 解决get和post请求 全部乱码的过滤器 */
public class GenericEncodingFilter implements Filter {
  @Override
  public void destroy() {}

  @Override
  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
      throws IOException, ServletException {
    // 处理response的字符编码
    HttpServletResponse myResponse = (HttpServletResponse) response;
    myResponse.setContentType("text/html;charset=UTF-8");

    // 转型为与协议相关对象
    HttpServletRequest httpServletRequest = (HttpServletRequest) request;
    // 对request包装增强
    HttpServletRequest myrequest = new MyRequest(httpServletRequest);
    chain.doFilter(myrequest, response);
  }

  @Override
  public void init(FilterConfig filterConfig) throws ServletException {}
}

// 自定义request对象，HttpServletRequest的包装类
class MyRequest extends HttpServletRequestWrapper {

  private HttpServletRequest request;
  // 是否编码的标记
  private boolean hasEncode;
  // 定义一个可以传入HttpServletRequest对象的构造函数，以便对其进行装饰
  public MyRequest(HttpServletRequest request) {
    super(request); // super必须写
    this.request = request;
  }

  // 对需要增强方法 进行覆盖
  @Override
  public Map getParameterMap() {
    // 先获得请求方式
    String method = request.getMethod();
    if (method.equalsIgnoreCase("post")) {
      // post请求
      try {
        // 处理post乱码
        request.setCharacterEncoding("utf-8");
        return request.getParameterMap();
      } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
      }
    } else if (method.equalsIgnoreCase("get")) {
      // get请求
      Map<String, String[]> parameterMap = request.getParameterMap();
      if (!hasEncode) { // 确保get手动编码逻辑只运行一次
        for (String parameterName : parameterMap.keySet()) {
          String[] values = parameterMap.get(parameterName);
          if (values != null) {
            for (int i = 0; i < values.length; i++) {
              try {
                // 处理get乱码
                values[i] = new String(values[i].getBytes("ISO-8859-1"), "utf-8");
              } catch (UnsupportedEncodingException e) {
                e.printStackTrace();
              }
            }
          }
        }
        hasEncode = true;
      }
      return parameterMap;
    }
    return super.getParameterMap();
  }

  // 取一个值
  @Override
  public String getParameter(String name) {
    Map<String, String[]> parameterMap = getParameterMap();
    String[] values = parameterMap.get(name);
    if (values == null) {
      return null;
    }
    return values[0]; // 取回参数的第一个值
  }

  // 取所有值
  @Override
  public String[] getParameterValues(String name) {
    Map<String, String[]> parameterMap = getParameterMap();
    String[] values = parameterMap.get(name);
    return values;
  }
}
